261228778 has 4 divisors (see below), whose sum is σ = 391843170. Its totient is φ = 130614388.

The previous prime is 261228763. The next prime is 261228787. The reversal of 261228778 is 877822162.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 211906249 + 49322529 = 14557^2 + 7023^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 65307193 + ... + 65307196.

Almost surely, 2^261228778 is an apocalyptic number.

261228778 is a deficient number, since it is larger than the sum of its proper divisors (130614392).

261228778 is a wasteful number, since it uses less digits than its factorization.

261228778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130614391.

The product of its digits is 150528, while the sum is 43.

The square root of 261228778 is about 16162.5733718366. The cubic root of 261228778 is about 639.2543219613.

The spelling of 261228778 in words is "two hundred sixty-one million, two hundred twenty-eight thousand, seven hundred seventy-eight".